/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.tsfile.utils;

public class BitConstructor {

    private static final int BITS_IN_A_BYTE = 8;
    private static final long ALL_MASK = -1;
    private final ByteArrayList data;
    private byte cache = 0;
    private int cnt = 0;

    public BitConstructor() {
        this.data = new ByteArrayList();
    }

    public BitConstructor(int initialCapacity) {
        this.data = new ByteArrayList(initialCapacity);
    }

    public void add(long x, int len) {
        x = x & ~(ALL_MASK << len); // Make sure that all bits expect the lowest len bits of x are 0
        while (len > 0) {
            // Number of bits inserted into cache
            int m = len + cnt >= BITS_IN_A_BYTE ? BITS_IN_A_BYTE - cnt : len;
            len -= m;
            cnt += m;
            byte y = (byte) (x >> len);
            y = (byte) (y << (BITS_IN_A_BYTE - cnt));
            cache = (byte) (cache | y);
            x = x & ~(ALL_MASK << len);
            if (cnt == BITS_IN_A_BYTE) {
                pad();
            }
        }
    }

    public byte[] toByteArray() {
        byte[] ret;
        if (cnt > 0) {
            data.add(cache);
            ret = data.toArray();
            data.removeAtIndex(data.size() - 1);
        } else {
            ret = data.toArray();
        }
        return ret;
    }

    public void clear() {
        data.clear();
        cache = 0x00;
        cnt = 0;
    }

    /**
     * Fill the rest part of cache with 0
     */
    public void pad() {
        if (cnt > 0) {
            data.add(cache);
            cache = 0x00;
            cnt = 0;
        }
    }

    public void add(byte[] bytes) {
        if (cnt == 0) {
            data.addAll(bytes);
        } else {
            for (byte aByte : bytes) {
                add(aByte, 8);
            }
        }
    }

    public int sizeInBytes() {
        return data.size() + (cnt > 0 ? 1 : 0);
    }
}
